Testing virucidal activity in Germany: an update

Several chemical disinfectants have been tested in a quantitative suspension test for virucidal activity as per the test method devised by the German Society for Control of Viral Diseases (DVV) and the former German Federal Health Office (BGA, now the Robert Koch-Institute, RKI) drafted in 1982. The introduction of the term “limited virucidal activity” (effective against enveloped viruses) in addition to the existing term “virucidal activity” (effective against non-enveloped and enveloped viruses) by the Robert Koch Institute has led to enormous expansion of these tests. However, there are no definitions to determine when a disinfectant with virucidal activity as apposed to a disinfectant with limited virucidal activity is to be used. The 1982 guideline was recently revised, while bringing it into line to reflect the latest insights. The BSA challenge has been omitted, while other controls such as verification of the sustained effect and interference control with which cell susceptibility is verified have been incorporated. A new requirement is that all tests be conducted in at least two independent batches, followed by biometric evaluation of the test results with calculation of the 95% confidence interval. The new guideline differs from DIN EN 14476, which in the meantime has been published in Europe, in that it does not feature the statistics now required. This guideline has introduced the parvovirus for chemothermal inactivation as well as the Bovine Viral Diarrhea Virus (BVDV) as test virus for the limited virucidal activity (in addition to vaccinia virus which serves as a surrogate virus for hepatitis C virus – HCV). A second important example is Feline Calicivirus (FCV), which serves as a surrogate for noroviruses. In the USA efficacy testing of surface disinfectants against noroviruses is conducted with FCV in a carrier test (practice-related test). The third surrogate virus is the Duck Hepatitis B Virus (DHBV), used as a surrogate for hepatitis B virus (HBV). Today evaluation of the virus-inactivating properties is often conducted in parallel with bacteriological evaluation, so as to avoid any subsequent surprises in respect of viral efficacy. The DVV has failed over the past 24 years to formulate guidelines for practice-oriented tests. The future challenge is to define these as quickly as possible. Here similar approaches should be used for e.g. process challenge devices, challenge, exposure time as for bacteriological evaluation, so that the resultant application recommendations have equivalent status. The term “limited virucidal activity” should be expanded to disinfectant efficacy at European level.